Medical devices, e.g., probes, are used in a variety of applications. Such probes are frequently inserted into the human body as part of medical procedure. Probes are often relatively expensive durable devices. In many cases, absent the risk of disease transfer and/or infection, probes may be used repeatedly. Unfortunately, a probe's shape and/or construction can make it difficult to sterilize thoroughly between uses.
For purposes of avoiding infection and the problems associated with sterilizing a probe thoroughly a sterile sheath may be used to cover the portion of the probe which is inserted into the human body. After each use, the used sheath is discarded and replaced with a new sterile sheath thereby allowing reuse of the probe at a minimal cost.
In cases of medical probes where thermal conductivity is important, e.g., cryogenic probes and/or temperature sensing probes, the sheath should not interfere significantly with the transfer of heat to/from portions of the probe where thermal transfer is intended to occur.
One example of a medical probe that may use a sheath is a cryogenic probe such as the probe 100 shown in FIG. 1. The probe 100 comprises a handle 102, a hollow tubular cannula 106, and a cold tip 108. The cold tip 108 is used to absorb heat from any tissue with which it contacts thereby cooling and potentially freezing the contacted tissue. Thus, in the known probe 100, heat transfer is to occur at the tip 108. However, heat transfer is intended to be limited elsewhere to prevent the unintentionally freezing of tissue contacting the cannula 106.
A sterile sheath may be placed over the probe 100 to protect the probe from contamination, and to protect the patient from possible infection. Preferably, the sheath has a thermally conductive region that covers the cold tip 108, and a nonconductive or less conductive region corresponding to the portion of the sheath intended to surround the cannula 106.
In order to insure good thermal conductivity at points where heat transfer is desired, there should be a snug fit between the sheath and the probe. In order to enhance thermal transfer between the sheath and probe at the desired points a thermal conductive medium (TCM), e.g., thermally conductive grease, may be applied to the inside of the sheath.
Known techniques for applying TCM to the interior of a sheath involve manually applying a TCM to the conductive region, e.g., tip, of the sheath using a hand held wand brush. In the known method, the TCM is first applied to the wand brush and then the brush is inserted into the tip of the sheath transferring the TCM to the inside of the sheath's tip. This method leads to variability in the amount of TCM applied to the sheath and can lead to the problems discussed above associated with TCM lumps and excessive TCM application. In addition to problems relating to variability in TCM application, the known TCM application procedure has the disadvantage of being time consuming to perform.
In view of the above discussion, it can be appreciated that there is a need for improved methods and apparatus for applying TCM to specific portions of a sheath. It is desirable that any new TCM application methods produce more reliable and uniform application of TCM to the intended portions of the sheath. It is also desirable that any new TCM application methods reduce the amount of time associated with performing the TCM application process.